This application is for support to purchase a Leica AM TIRF (total internal reflection fluorescence) microscope system. The instrument will be housed within the - Facility of the Kimmel Cancer Center of Thomas Jefferson University. This Facility provides light microscopy services to users within the Kimmel Cancer Center, throughout Thomas Jefferson University, and as needed and available to investigators at neighboring research institutions. There is no TIRF facility presently available at Thomas Jefferson University. In TIRF mode, the requested instrument will provide the ability to image plasma membrane structures, vesicle transport to and from the plasma membrane and other membrane activities, as well as single molecules with exceptionally high sensitivity and low background. The TIRF illumination is complemented by sensitive widefield epifluorescence imaging, which will also provide excellent FRET capability. Equipped with multiple laser lines and fast AOTF wavelength switching, these attributes are uniquely suited to the users'needs for rapid imaging of live cells. The TIRF system is vitally needed to support the research programs of eight major users drawn from five Departments (Biochemistry and Molecular Biology, Cancer Biology, Medicine, Microbiology and Immunology, and Physiology) and two Research Centers (Kimmel Cancer Center, Center for Translational Medicine) of Thomas Jefferson University. All of the selected major users have ongoing and well-funded research programs, as well as experience and expertise with fluorescence and confocal microscopy of live and fixed cells. In addition, the instrument will serve other more occasional users within the Kimmel Cancer Center who have expressed interest in TIRF microscopy, as well as other research investigators of Thomas Jefferson University. PUBLIC HEALTH RELEVANCE: The plasma membrane is the interface that is key to the transfer of information and material between the cell and its environment. The Leica AM TIRF microscope requested in this proposal is uniquely specialized for investigating this critically important cellular domain, and studies carried out with this instrument will provide important insight into a variety of diseases including cancer, cardiovascular disease, neurological disorders, and infectious diseases. These disease areas encompass the major research strengths and long-range biomedical goals of Thomas Jefferson University.